Heretofore, there has been known an energy supply technique that charges a storage battery mounted in a vehicle, using microwave. This energy supply technique supplies electric power to magnetrons from a microwave power source in an electric supply apparatus placed on the ground such as a parking lot and causes the magnetrons to generate microwaves. The microwaves generated from the respective magnetrons are sent through respective electric transmission antennas to an electric reception apparatus disposed at the bottom surface of the vehicle. The microwaves received by the electric reception apparatus are converted into electric power, rectified to be converted into DC electric power, and then supplied to the storage battery.
Meanwhile, such an energy supply technique has a problem in that, when there is an obstacle between an electric supply side and an electric reception side for microwaves, this obstacle decreases the transmission efficiency of microwaves. In addition, when the obstacle is a living thing, such as a human or an animal, the living thing is affected by the microwaves.
As a method of solving such problems, a method of detecting whether there is an obstacle between the electric supply side and the electric reception side is disclosed in Patent Literature (hereinafter, abbreviated as PTL) 1. PTL 1 discloses a technique for temporarily stopping electric transmission when the transmission efficiency of electric power supplied in a contactless manner from the electric transmission unit to the electric reception unit is less than a specified value. This is because there may be an obstacle between the electric transmission unit and the electric reception unit in this case.